title: Bacterial effects on arbuscular mycorrhizal fungi and mycorrhiza development as influenced by the bacteria, fungi, and host plant.
abstract: Bacterial strains from mycorrhizal roots (three belonging to Comamonadaceae and one to Oxalobacteraceae) and from non-mycorrhizal roots (two belonging to Comamonadaceae) of Medicago truncatula and two reference strains (Collimonas fungivorans Ter331 and Pseudomonas fluorescens C7R12) were tested for their effect on the in vitro saprophytic growth of Glomus mosseae BEG12 and on its colonization of M. truncatula roots. Only the Oxalobacteraceae strain, isolated from barrel medic mycorrhizal roots, and the reference strain P. fluorescens C7R12 promoted both the saprophytic growth and root colonization of G. mosseae BEG12, indicating that they acted as mycorrhiza helper bacteria. Greatest effects were achieved by P. fluorescens C7R12 and its influence on the saprophytic growth of G. mosseae was compared to that on Gigaspora rosea BEG9 to determine if the bacterial stimulation was fungal specific. This fungal specificity, together with plant specificity, was finally evaluated by comparing bacterial effects on arbuscular mycorrhizal symbiosis when each of the fungal species was inoculated to two different plant species (M. truncatula and Lycopersicon esculentum). The results obtained showed that promotion of saprophytic growth by P. fluorescens C7R12 was expressed in vitro towards G. mosseae but not towards G. rosea. Bacterial promotion of mycorhization was also expressed towards G. mosseae, but not G. rosea, in roots of M. truncatula and L. esculentum. Taken together, results indicated that enhancement of arbuscular mycorrhiza development was only induced by a limited number of bacteria, promotion by the most efficient bacterial strain being fungal and not plant specific.
authors.affiliation: Università del Piemonte Orientale 'Amedeo Avogadro', I-15100, Alessandria, Italy.|INRA, Université de Bourgogne, UMR 1229 'Microbiologie du Sol et de l'Environnement', CMSE, 21065, Dijon, France.
authors.forename: Barbara
authors.initials: B
authors.lastname: Pivato
authors.affiliation: INRA, Université de Bourgogne, UMR 1229 'Microbiologie du Sol et de l'Environnement', CMSE, 21065, Dijon, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Offre
authors.affiliation: Università del Piemonte Orientale 'Amedeo Avogadro', I-15100, Alessandria, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Marchelli
authors.affiliation: Università del Piemonte Orientale 'Amedeo Avogadro', I-15100, Alessandria, Italy.
authors.forename: Bruno
authors.initials: B
authors.lastname: Barbonaglia
authors.affiliation: INRA, Université de Bourgogne, UMR 1229 'Microbiologie du Sol et de l'Environnement', CMSE, 21065, Dijon, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Mougel
authors.affiliation: INRA, Université de Bourgogne, UMR 1229 'Microbiologie du Sol et de l'Environnement', CMSE, 21065, Dijon, France. philippe.lemanceau@dijon.inra.fr.|UMR Microbiologie du Sol et de l'Environnement, INRA/Université de Bourgogne, CMSE, BP 86510, 21065, Dijon cedex, France. philippe.lemanceau@dijon.inra.fr.
authors.forename: Philippe
authors.initials: P
authors.lastname: Lemanceau
authors.affiliation: Università del Piemonte Orientale 'Amedeo Avogadro', I-15100, Alessandria, Italy.
authors.forename: Graziella
authors.initials: G
authors.lastname: Berta
mesh_terms: D018407:Bacterial Physiological Phenomena; D005658:Fungi / Q000254:growth & development* / Q000502:physiology; D038821:Mycorrhizae / Q000254:growth & development* / Q000502:physiology; D018521:Plant Physiological Phenomena; D018517:Plant Roots / Q000382:microbiology* / Q000502:physiology; D010944:Plants / Q000382:microbiology*; D013045:Species Specificity; D013559:Symbiosis